Telephone-exchange apparatus and system.



J. ERIGKSON.

TELEPHONE EXCHANGE APPARATUS AND SYSTEM.

APPLICATION FILED JULY 31, 1906.

Patented Jan.5, 1915.

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W WM W W w 1% A 5 @m J. ERIOKSON.

TELEPHONE EXCHANGE APPARATUS AND SYSTEM.

APPLICATION FILED JULY 31, 1906. Patented Jan. 5, 1915.

2 SHEETS-SHEET 2.

@XWZE 6 02654027 WlTEU STATES PATENT UFWl@E.

JOHN ERICKSON, OF CHICAGO, ILLINOIS, ASSIGNOR, BY MESNE ASSIGNMENTS, T0 FIRST TRUST AND SAVINGS BANK, TRUSTEE,

OF CHICAGO, ILLINOIS.

rieaaoc.

I Specification of Letters Patent.

Patented Jain. 5, 1915.

Application filed July 31, 1906. Serial No. 328,547.

1 '0 all whom it may concern:

Be it known that 1, JOHN ERICKSON, a citizen of the United States of America, and resident of Chicago, Cook county, Illinois, have invented a certain new and usefulImprovement in Telephone-Exehange Apparatus and Systems, of which the following is a specification.

My invention relates to telephone systems in general, but more particularly to automatic or semi-automatic telephone exchange systems, and especially to automatic or semiautomatic systems in which automatic switching machines, such as selectors and connectors, are employed by calling sub scribers for establishing connection with the lines of called subscribers, or with any other suitable lines, and in which repeaters are provided for use in trunking between exchanges, or for successively controlling a second-selector and a connector, or other s table switching machines, wherever the distance or length of a circuit renders the resistance so great as to make it undesirable for a calling subscriber to transmit electrical impulses over the entire circuit, it being preferable in such cases to employ a repeater in the circuit and thus repeat or relay electrical impulses from one section thereof to another.

Generally stated the object of my invention is the provision of an improved and highly efficient telephone exchange system in which improved means are provided for repeating or relaying switch operating or other electrical impulses from one section of a line circuit to another.

Special objects of my invention are the provision of improved means for preventing the condensers, or such other reactive devices as may be employed in the repeater, from causing, by kicks or static discharges, confusion or uncertainty in the operation of the switch or switches controlled by the repeater, such, for example, as a second-selector and connector, thus rendering unnecessary the delicate or particular adjustment wh ch would otherwise be found necessary, perhaps, for theline relays of the said selector and connector, or for other parts of the system: the provision of a repeater having line relays adapted when energized to open the parallel conductors of the trunk line leading to the switch or switching machine to be controlled by the calling subscriber through the medium of such rela s, whereby the condensers or other reactive devices employed in the repeater will not be connected with the said trunk line when the relays are energized. and whereby a such time no discharge can take place from the condensers over the trunk line, thus insuring the desired certainty of action on the part of the switching machine to which the trunk line leads, without resorting to such particular or delicate adjustment of various'parts of the system as might otherwise be found necessary; and the provision of certain details and features of improvement and combinations tending to increase the general efficiency and serviceability of a telephone exchange system of this particular character.

This application shows and describes repeater apparatus similar to that which is shown and which is being claimed in my copending applications Serial Numbers 326,450 and326,931. In this application the springs of the line relays in the repeater mechanism directly control the continuity of the talking circuit, while-in the above mentioned copending applications the line relays in the repeater mechanism control the intervening mechanism which in turn controls the continuity of the talking circuit.

To the foregoing and other useful ends, my invention consists in matters hereinafter set forth and claimed.

In the accompanying drawings. Figure 1 is a diagram showing a subscribers line connecting the sub-station A (#6000) with its allotted first-selector B and a re eater C. Fig. 2 shows in diagram a called substation ]D (#2220), a first-selector E allotted to the called line, a connector-switch F and a second-selector G. Fig. 1 represents the apparatus of exchange #1, and Fig. 2 represents the apparatus of a second exchange, which latter will be designated as central #2. Figs. 1 and 2 taken together represent an established connection between the subscribers A and l) in a system embodying the principles of my invention.

o It will be noticed that the apparatus is shown inan operated condition. maintaining the connection between the two substations. Each central oihce has its own battery, the central office #1 having its battery B with its positive terminal preferably grounded at G, and the central oiiiice #2 having its battery B with its positive terminal preferably grounded at G2. These batteries may be of any suitable voltage. but good results are obtained when they are built to supply a current of from fifty to fifty-five volts. The substation may be of any suitable or approved type. The substation shown in Fig. 1 is, as usual. provided with a receiver 2, transmitter 3, ringer 4:, induction-coil 5, switch-hook 6, impulse wheel 7, cam latch 8 for normally locking the dial,acam dog 9 and a battery 10. The impulse wheel 7 is, of course,provided with a set of vertical impulse teeth 11 and a rotary impulse tooth 12 for operating, respectively, the verticalimpulse spring 13 and the rotary impulse spring 14: with respect to the ground post 15. The substation ground Gr is permanently connected to the ground spring 16. which latter is held normally away from the ground spring 17 by the insulating tip 18 upon the end of the cam latch 8. Said insulating tip normally rests opposite the angled terminal of the ground spring 16, as shown at substation D (Fig. 2), and also when the hook first rises. It will be under stood. of course, that the subscribers dial (which is not shown), the impulse wheel 7 and the cam dog 9 are all rigidly secured to the shaft 19. While the receiver is on the switch-hook the switch hook cam arm 20 removes the ground spring 16 from the insulating tip 18, so that the cam latch 8 falls in front of the pin 21 on the end of the cam dog 9, and it thus becomes impossible to rotate the dial. When the receiver is removed, however, the switch-hook is raised by a suitable spring (not shown) and the cam-arm 20 by engaging the face 22 of the cam latch 8 raises the latter sulficiently to permit the pin 21 to pass under the cam latch when the dial is sufiiciently rotated. The ground spring 16, when the cam arm 20 leaves its normal position, falls against the insulating tip 18 and remains there and out of engagement with the other ground spring 17 until the dial is rotated, since the cam arm 20 does not raise the cam latch 8 sufficiently to permit the tip 18 to clear the angled section on the end of the ground spring 16. The extreme end of the cam latch 8, which is engaged by the cam dog pin 21. is rounded off in such manner that when the dial is rotated the pin 21 slides beneath the said rounded section and raises the cam latch 8 a trifle more, so that the insulating tip 18 may now leave the ground spring 16, permitting the latter to engage the ground spring 17 and thus establish connection between ground Gr and the ground post 15. When the receiver is on the hook the cam 23 engages the spring 24 and thereby closes the ringer 4 across the line. By engaging the said spring the said cam arm 23 not only closes the substation ringing circuit, but by separating the springs 25 and 26 opens the local circuit, and by separating the springs 27 and 28 opens the secondary circuit for removing the receiver 2 from across the line. But when the switch-hook is up it naturally follows that the primary circuit is closed, the ringer is ofl? the line, and the secondary circuit comprising the receiver 2 is bridged across the line. However, while the dial is being operated and, therefore, while the cam 29 of the cam dog 9 is out of normal position. the secondary circuit is opened at the point between the springs 27 and 28. so that no electric impulses that may be delivered to either of the subscribers line conductors individually shall pass through the receiver to the other side of the line. The switch hook cam 30 is provided for controlling the release springs 31, 32 and 33, which release springs are pressed into contact, grounding the subscribers line conductors simultaneously when it becomes desirable to release the central oilice switching apparatus. The signaling button 34 has the office of controlling the spring 35 that normally rests in engagement with the contact point 36, but from which it is separated and carried into engagement with the ground contact 37, whereby only the vertical side of the subscribers line may be grounded when signaling. With this apparatus the subscriber, when he wishes to make a call, removes his receiver from the switch-hook and thereby disconnects the ringer from across the line, closes his local talking circuit and connects his secondary circuit across the line. He then operates his dial once for each digit of the number he is to call. At the operation of the dial for the first digit connection is made between the substation ground G and a ground post 15, and the secondary circuit is opened between the springs 27 and 28 at the forward motion of the dial. At the return motion of the dial the subscribers vertical line conductor is grounded a number of times equal to the numerical value of the first digit and then the rotary side of the line is grounded once and then the secondary circuit is again closed between the springs 27 and 28. Upon the second operation of the dial the secondary circuit is again opened (at the same point) at the forward motion of the dial, and upon the return motion of the dial the vertical line conductor is grounded a number of times equal to the numerical value of the second digit: then the rotary side of the line is grounded once, and then the secondary circuit is again closed. Each succeeding operation of the dial accomplishes the same result accomplished by the second operation of the dial. The number having been called the signaling button 34 is then pressed, whereby the secondary circuit is '35 magnet side switch wiper 48.

transect opened between the spring 35 and contact point 36, and the vertical side of the line is grounded when the spring 35 engages the contact point 37. It the called" subscriber is not busy, the pressing of the signaling button rings the called subscribers'substation bell; but if his line is busy a busy signal will be sent back to the calling subscriber. When a subscriber is through talking, by hanging up his receiver he presses the release springs 31. 32 and 33 into contact for a moment, grounds the subscribers line conductors simultaneously for a moment, and this restores all the switching apparatus that has been brought into service bV him.

The first-selector may be of any suitable or approved type, such, for example, as selector of the general type described in Patent No. 815.321, granted March 13. 1906, to Keith, Erickson and Erickson. The subscribers vertical and rotary lineconduc tors 38' and 39, respectively, are permanently connected with the vertical and rotary line relays 40 and 41. The side switch wipers42 and 43. respectively, are also connected with the line conductors 38 and 39, the former wiper being normally in engagement with the contact point 44 and the latter wiper with the contact point 45. The side switch, as is well known, comprises besides the side switch wipers 42 and 43 the private side switch wiper 46, the vertical magnet side switch wiper 47 and the rotary The side switch is controlled by the private magnet 49. and in the normal or first position of the side switch the side switch wipers 42, 43, 46, 47 and 48' engage with the contact points 44, 45. 50. 51 and 52. respectively; in the second position they rest on the contact points 53, 54, 55, 56 and 57, respectively; and in the third position in engagement with the contact points 58, 59. 60, 61 and 62, respectively, Through the medium of the vertical line relay 40, and while the side switch is in first position. the subscriber controls the vertical magnet 63, which latter operates the switchshaft vertically, which shaft (not shown)" carries the linewiners 64 and 65 and the private wiper 66. Through the medium of the rotary line relay 41 the subscriber con-' trols the private magnet 49a'nd, therefore, the side switch. When the side switch is in second position therotary magnet 67 is energized and the switch-shaft; that carries the wipers 64, 65 and'66 is operated in a rotary direction. The vertical and rotary line relays 40 and 41 provide the means by which the release magnet 68 is controlled by the subscriber. The switch-shaft of the selector B carries a so-called normal post arm 69 wh ch, when the'shatt-is in an od-normal position, permits the spring 70 to engage the:

contact point 71 and thereby me a connec- 73 leads to the connector private bank, and

by way of said private normal conductor the bridge-cut-ofl' relay 74 is energized whenever any subscriber calls the substation A. Said relay 74 is provided to control the connection between. the vertical and rotary line relays 40 and 41 and the battery 13. lit is customary to thus disconnect said relays" from the battery and from across the line, whenever the line allotted to the selector is called, for well known reasons. Said connection is controlled by the bridge-cut-ofi' relay 74 through the medium of the springs which it controls or operates.

The repeater C is a comparatively simple apparatus. being provided with a vertical line relay 79 and a rotary line relay 80. The relay 79', by means of its armature 81, is adapted to control the springs 82, 83 and S4. ln a similar manner the rotary line relay 80. by means of the armature 85, is adapted to control the springs 86, 87 and 88. As shown, the trunk conductors 89 and 90, that connect the repeater C at exchange #1 with the second-selector G at the exchange #2. terminate respectively in the repeater springs 83 and 87. said conductorsbeing normally maintained in connection 'with the repeater condensers 91 and 92, and through said condensers with local trunk conductors 93 and 94 that lead-to the selector banks. The vertical line relay 79 by operating is adapted to disconnect the trunk conductor 89 from the condenser 91 and to ground the said conductor on the spring 84. lln a similar manner the rotary line relay is adapted to disconnect the rotary trunk conductor from the condenser 92 and to connect itinstead with the ground spring 88. The repeater as a whole may be assembled upon a suitable base which may be located at any? desirable point.

The second-selector G is the same as the" first-selector B with the exception that there are no normal conductors. such. as the normal conductors 95 and 96 (Fig.1), to be Since like parts are likewise represented throughout the drawings, the vertical magnet 97 and the rotary magnet 98, the release &

105, the said private magnet also controls the circuit of the release magnet 99 and of the vertical magnet 97 in the usual manner by means of the springs 106, 107 and 108;

The vertical movementof the switch-shaft, and therefore of the wipers 109, 110 and 111, is controlled by the vertical magnet 97, and

the rotary movement by the rotary magnet 98, the said rotary magnet circuit being provided with the usual interrupter springs 112. The switch-shaft is provided with a normal post arm 113 for controlling the switch shaft springs 114 and 115 and, therefore, the energizing circuit for the off-normal lamp 116. The operating magnets of the switch are controlled'by the subscriber through the medium of the vertical and rotary line relays 117 and 118, as is well known. Said relays have under their control the usual springs 119, 120 and 121.-

The connector-switch'F may also be of any suitable or approved type, such, for example, as the general type of connector described in Patent' No. 815,176, granted March 13, 1906, to Keith, Erickson and Erickson. The mechanical details of the selector and connector, as is wellknown, are very much the same, although there is some material difference in the circuits. The connector switch shaft (not shown), like the shaft of the selectors, ca rriesthe usual line wipers 122 and 123 and the private wiper 124'. The connector-switch is also con- 1 trolled by the calling subscriber through the medium of the vertical and rotary line relays 124 and 125. The vertical line relay 124 directly controls the vertical magnet .126 and and a third position. -In normal positionalso the rotary magnet 127. The office of the'said vertical magnet 126 is to give the shaft and the shaft wipers their vertical movement, and the rotary magnet 127 imparts to'the said shaft a rotaryor circular movement. The rotary line relay 125 controls the private magnet 128, which latter under certain conditions controls in turn the vertical and rotary magnets 126 and 127 and the release magnet 129, and alsothe side switch-wipers 130, 131, 132 and 133, all of which are shown. The'said side switch, like the side switch of the first-selector, has a normal or first position. a second position 7 the "respective side switch wipers engage the contact points 134, 135, 136 and 137 in secend position the contact points 138, 139, 140

d141, and in third position the contact -,j;bints 142, 143, 144 an-l 145. The release ",magn'et 129 is also controlled by the line relays 124 and'125 conjointly and by the back-bridge relays 146 and 147 conjomtly;

' duced in the primary winding 155 of the said induction-coil 154. Said primary winding 155 is connected to the contact point 156 against which'the switch shaft spring 157 is allowed to press when the normal post arm 158 is raised.

The first-selector E of the called line is the same as the first-selector B and needs, therefore, no description. The substation D is also the same assubstation A.

The connection between the two exchanges may be arranged in any convenient manner, and I do not limit myself to any particular arrangement, since the system herein,disclosed is variable. sumed that the maximum number of subscribers to be accommodated at the exchanges #1 and #2 is five thousand, then the first five levels of the first-selectors at exchange #1 may be limited to, local connections, and the last five levels to trunk connections to exchange #2, each of which trunk connections, of course, comprising a repeater similar to the repeater C. The reverse would be the arrangement for exchange #2, for in that exchange the first five levels would be limited to trunk-operations to exchange -#1, and the last five levels to localconnections. I do not limit myself to this arrangement even when the maximum number to be accommodated at each exchange is not to exceed five hundred. It will be understood, of course, that all of the switches maybe arranged in groups. For example, the first-selectors of the same group all'have similar bank contacts connected'in-multiple. If each group consists of one hundred selectors there will be one hundred banks and, therefore, one hundred vertical contacts in multiple, one hundred rotary contacts in multiple, and one hundred corresponding private contacts in multiple, for each subscribers telephone line. Therefore, if any one of the selectors of a given-hundred'connect with the repeater C a guarding potential will be established at the private wiper 66 and at all other private contacts in multiple, so that all other selectors of that group, if they make a call, will pass over the trunk that leads to the repeater G without interfering with the connection. The same grouping arrangement,

If it is asas is well known, applies to the central oflice #2 as well, and applies not only to the firstselector but also to all the switches.

The operation in detail is as follows: To call the number 2220 the subscriber at substation A, as previously described, operates the dial once for each digit. The first operation of the dial results in grounding the vertical line conductor 38 twice, and as a result the vertical line relay 40 of the firstselector B is energized twice, the current flowing in each case from ground G through the ground springs 16 and 17 to the ground post 15, thence through the vertical impulse spring 13 to the vertical line conductor 38, vertical line relay 40, bridge-cut ofi' relay springs 159 and 160 to the battery lead 161, and through battery B to ground G Each time that the vertical line relay 40 is energized the line relay springs 162 and 163 are pressed into contact and an energizing circuit is thereby established through the vertical magnet 63. Current through. the said magnet flows from ground G through the springs 163 and 162, private springs 164 and 165, side switch Wiper 47, contact point 51, vertical magnet 63 to the battery lead 161, and through battery 13 to ground U The vertical magnet 63 then operates to raise the shaft for placing the wipers 64, 65 and 66 on a level with the contact points at which the trunk line conductors that lead to the repeater C terminate. When the rotary line conductor 39 is grounded the rotary line relay 41 is energized in turn. The current through said relay flows from ground Gr to the ground post 15, thence through the rotary impulse spring 14 to the rotary line conductor 39, through the rotary line relay 41, bridge-cutoii relay springs 166, 159 and 160 to the battery lead 161, thence through battery B to ground G The rotary line relay in turn operates to energize the private magnet 49 by establishing a local circuit through the line relay springs 167 and 163. The current "for energizing the private magnet flows from ground G through the line relay springs 163 and 167 to the private magnet 49, thence through battery lead 161 and through battery B to ground G The private magnet 49 then operates to release the.

side switch from first to second position, and as a result a local circuit is closed through the rotary magnet 67 when the side switch wiper 48 engages the contact point 57. The current through the rotary magnet flows from ground 6 to the contact point 57, thence through the side switch wiper 48, interrupter springs 168 and 169, rotary magnet 67 to the battery lead 161, thence through battery B to ground G The rotary magnet is energized step by step and the wipers 64, 65 and 66 are advanced in like manner over busy contact points until the wipers find the first idle trunk line, which, it is assumed, is the trunk line that leads to the repeater C.

As long as the private wiper 66 is passing over busy contact points the private magnet 4-9 is retained energized and the side switch is locked in second position, as is well known, until all guarding points are passed. The current through the private magnet, while the private wiper 66 is passing over busy contacts, flows from the grounded terminal (l of the battery 13 through the occupying switch to the private Wiper 66, thence through the side switch wiper 46, contact point 55, private magnet 49 to the battery lead 161, thence through battery B to ground G At the instant that the private magnet 49 deenergizes, after the private wiper passes over busy contacts, the side switch is tripped into third position; or it there are no busy contacts to be paszed over, the rotary magnet 67, as is well known, trips the side switch to third position, with the result that as soon as the side switch wipers 42 and 43 engage the contact points 58 and 59, respectively, the subscribers line conductors 38 and 39 are extended to the repeater C. Also, since the side switch wiper 46 at the same time engages the contact point 60 a guarding potential is established at the private wiper 66 to protect the seized trunk line that leads to the repeater C from being disturbed by any other switch. The

second operation of the dial, since the line is now extended, is directed to the secondselector (.i. Grounding the vertical line conductor 38 twice energizes the vertical line repeater relay 79 twice, the current flowing in this case from ground G3 to the ground post 15, thence through the vertical impulse spring 13 to the vertical line conductor 38, side switch wiper 42 of the selector B, vertical line wiper 64, vertical line relay 79 of the repeater C to the battery lead 161, and through battery B to ground G Each time thatthe said vertical line relay 79 is energized the springs 83 and 84 are pressed into contact. The closure of contact between said springs grounds the vertical trunk conductor 89. This, of course, occurs each time that the vertical line relay 79 is operated. Grounding the vertical trunk conductor 89 in turn operates the switches at the exchange #2, which operation will hereinafter be considered. When the subscriber grounds the rotary line conductor 39 he energizes the rotary line relay 80 of the repeater C, the current flowing from ground G to the ground spring 15, thence to the rotary impulse spring 14, rotary line conductor 39, first-selector side switch wiper 43, contact point 59, rotary line wiper 65, rotary line relav 80 to the battery lead 161,

thence through battery B to ground G The operation of the rotary line relay causes the line relay springs 87 and 88 to be pressed'together. The closure of the contact between the said springs sends a ground impulse to the rotary trunk conductor 90 for operating the switches at the second exchange. The vertical trunk conductor 89 termnates in the vertical line relay 117 (Fig. 2) of the second-selector G. Permanentiy connected to said trunk conductor is the side switch wiper 101, which wiper normally engages the contact point 170; but when the side switch passes to third position it engages the contact point 171. In a similar manner the rotary trunk conductor 90 terminates in the rotary line relay 118 of the said selector G. Permanently connected to the said trunk conductor is the side switch wiper 102, which wiper normally engages the contact point 172, and when the side switch is in third position it engages the contact point 173. Therefore, grounding the vertical trunk conductor 89 twice, as described in the preceding, operates the ver- 'tical line relay 117, the current flowing from ground Gr at the repeater C through the line relay springs 84 and 83 to the vertical trunk conductor 89, thence through the vertical line relay 117 to the battery lead 174, and through battery B to ground G The vertical line relay 117 in turn operates the vertical magnet 97, as described in connection with the first-selector B, so that the shaft wipers 109, 110 and 111 are raised to a level with the contacts from which a trunk conductor leads to the connector F. As soon as the switch-shaft rises the normal post arm 113 permits the switch shaft spring 114 to engage the contact point 115, so that the off-normal lamp 116 flashes up and indicates that the said switch is in use. The grounding of the rotary trunk conductor 90 in turn energizes the rotary line relay 118 of the second-selector G, which relay in turn energizes the private magnet 100 for a moment.

. The side switch of the second-seleetor then escapes from first to second positi'on. The current through the said rotary line relay 118 flows from ground G at the repeater C through the springs 88 and 87 to the rotary trunk conductor 90, thence through the rotary line relay 118 (Fig. 2) to the battery lead 174, and through battery B to ground G As soon as the side switch wiper 105 engages the second contact point an energizmg circuit is established through the retary magnet 98, which latter operates torotate the shaft in the same manner that the rotary magnet of the first-selector B operates the shaft thereof. The current through the said rotary magnet 98 flows from ground Gr through the side switch wiper 105, rotary magnet 98 and its allotted interrupter springs to the battery lead 174, and through battery B to ground G When the rotary magnet operates the side switch is tripped into third position, or if the wipers are carried over busy contacts the side switch does not pass to third position until the private magnet 100 deenergizes. As soon as the side switch passes to third position the side switch wipers 101 and 102 upon engaging the contact points 171 and 173, respectively, extend the trunk line conductors 89 and 90 to the connector F. At the same time the side switch wiper 103 engages the contact point 175 and a guarding potential is established at the private wiper 111 to prevent other switches from establishing connection with the connector F. The third operation of the dial, since the subscribers line conductors are extended to the connector F, are directed to the said connector. When the vertical line conductor 38 is grounded twice the vertical line relay 79 of the repeater C is again operated twice, whereby the vertical trunk conductor 89 is again grounded twice. Grounding the vertical trunk conductor 89 energizes the vertical line relay 124 of the connector. The current through said relav flows from ground Gr through the springs 84 and 83 to the vertical trunk conductor 89, thence through the side switch wiper 101, contact point 171, vertical line wiper 109 to the vertical line relay 124, thence to the battery lead 174 and from battery B to ground G The vertlcal line relay 124 in turn presses the line relay springs 188 and 189 into contact, and as a result the magnet 126 is operated. The current through the said magnet flows from ground Ur to the springs 189 and 188, private springs 190 and 191, side switch wiper 133, contact point 137, vertical magnet 126 to the battery lead 174, and through battery B to ground G'-. The vertical magnet 126, as usual, operates to raise the switchshaft. Being operated twice the shaft is raised two steps and the shaft wipers 122, 123 and 124 are carried to a level in which the line of the subscriber #2220 is located. When the rotary line conductor 39 is grounded once the rotary line relay 80 of the repeater C is energized once as before, and as a result the rotary trunk conductor 90 is grounded once, causing the rotary line relay 125 of the connector F to be operated. The current flows through the rotarv relay 125 from ground Gr through the springs 88 and 87 to the rotary trunk conductor 90, thence to the side switch wiper 102 of the second-selector G, contact point 173, rotary line wiper 110, rotarv line relay 125 to the battery lead 174, thence through battery B V maaaoo through battery I? to ground G The private magnet being operated momentarily causes the side switch to pass from first to second position. As a result the side switch wiper 133 shifts into engagement with the contact point 141, thus substituting the rotary magnet 127 for the vertical magnet 126 and placing the former under the control of the vertical line relay 124. The fourth operation of the dial causes the vertical line conductor 38 to be grounded again, the vertical line relay 79 of the repeater C to be energized again, and the vertical trunk conductor 89 to be grounded again, each ten times, since the fourth digit is the digit 0. Each time that the vertical trunk conductor 89 is grounded the vertical line relay 124 of the connector F is operated over circuits that have been pointed out; but instead of in turn operating the vertical magnet 126 it operates the rotary magnet 127 each time. lihe circuit through the said rotary magnet extends from ground (i to the side switch wiper 133, thence through the contact point 141 to the said rotary magnet 127, to the battery lead 174 and through battery B to ground G The switch-shaft is thus rotated step by step until the wipers 122, 123 and 124' are carried into connection with the normal conductors 193, 194 and 195 that extend to the first-selector E of the called the first-selector B line. The conductors 193 and 194 continue to the called subscribers line and to the substation #2220.- Grounding the rotary line conductor 39 for the last time energizes the rotary line relav 80 of the repeater C, which latter in turn grounds the rotary trunk conductor I 90 once. Grounding the rotary trunk conductor'90 energizes the rotary line relay 125 of the connector F, the energization of which relay causes either the release of the connector-switch, if the called line is busy, or the release of the side switch from second to third position, if the line is not busy, which latter operation places the side switch wipers 130 and 131 in engagement with the contact points 142 and 143, thus placing the calling subscribers line in connection with the called subscribers line through the condensers 148 and 149. This connection is marked by heavy lines in Figs.

1 and 2. It will be assumed, first, that the energization of the rotary line relay 125 produces the latter resultthat is, releases the connector side switch to third position.

It will be observed that the calling subscribers vertical line conductor 38 is connected through the vertical side switch wiper 42 and the vertical line wiper 64 of to the condenser 91, thence through the springs 82 and 83 to the vertical trunk conductor 89, thence through the side switch wiper 101 and vertical line wiper 109 of the second-selector G to the connector condenser 148, thence through the ringer relay springs 196 and 197, side switch wiper 130 to the vertical line wiper 122, normal conductor 193, called subscribers vertical line conductor 198, through the substation ringer 199 to the rotary line conductor 200, and back to the rotary normal conductor 194, line wiper 123, side switch wiper 131, ringer relay springs 201 and 202, condenser 149, line wiper 110, and side switch wiper 102 of the second-selector G, rotary trunk conductor 90, springs 87 and 86 of the repeater C, condenser 92, rotary line wiper 65 and side switch wiper 43 of the first-selector B to the rotary line conductor 39, thence through the receiver 2,. secondary winding 203 of the induction-coil 5 back to the vertical line conductor 38. To signal the called subscriber the calling subscriber presses his signaling button 34, thereby grounding the vertical line conductor 38 over a circuit that extends from ground G through the ground springs 16 and 17, conductor 204, contact point 37, spring 35 to the vertical line conductor 38. As a result the vertical line relay 79 of the repeater C is energized, which latter then grounds the vertical trunk conductor 89, in turn causing the energization of the vertical line relay 124 of the connector F. Said relay 124 (since the side switch wiper 133 is in third position) causes the ringer relay 150 to become magnetized. The current through said ringer relay flows from ground G to the side switch wiper 133, thence through the ringer relay 150 to the battery lead 174 and through battery 13 to ground G The ringer relay upon attracting its armature forces the ringer relay springs 201 and 197 onto the ringer relay springs 205 and 206, thus breaking the connection between the calling subscriber and the called subscriber and throwing the ringer generator 151 across the called subscribers line for ringing the bell 199 at the station of the latter. In order to prevent the ringing current from interfering with the line relays 207 and 208 of the called first-selector E the bridge-cutoif relay 209 is energized as soon as the connector side switch wiper 132 engages the grounded contact point 144. The circuit through said bridge-cut-ofl' relay extends from ground Gr through the side switch wiper 132 to the private wiper 124', thence through the side switch wiper 210 and contact point 211 to the bridge-cutoff relay 209, thence to the battery lead 174 and through battery B to ground G The said relay 209 upon energizing separates the springs 212, 213 and 214, thereby breaking the connection between the said relays 207 and 208 and battery lead, and between each other, leaving the line clear at the selector E. The same circuit that connects the side switch wiper 132 with the connector private protected by guarding potential established at the connector banks from the selector B of the calling line and the called line is protected by a guarding potential established at the connector. In either case if the line is busy, there is a guarding potential at the private bank contact that corresponds to the number of the busy line. It

' may be assumed, for example, that the called line #2220 is busy at the time that the rotary line relay 125 of the connector F is energized for the last digit. The busy release results when the rotary line relay presses the springs 215 and 216 into contact. As a result the release magnet 129 is placed in connection with the private wiper 124, which latter has been previously rotated onto a grounded contact. As a result there is sent a flow of current through the release magnet 129 from the private wiper 124 to the side switch wiper 132, which is now in second position, contact point 140, springs 216 and 215, release magnet 129 to the battery lead 174, and through battery B to ground G As a result the release magnet becomes magnetized and the connector switch is released and restored to normal condition. Then when the subscriber presses his signaling button and grounds the vertical line conductor 38 he energizes the vertical line relay 79 at the repeater C, grounds the vertical trunk conductor 89 and energizes the vertical line relay 12 1 of the connector. Since the side switch is now in first position, the connector having been released, the vertical magnet 126 is energized and the switch-shaft is raised so that the switch shaft springs 157 and 156 close connection. A circuit is thus established from the busy coil 155 of the busy machine H through the switch shaft 1 springs 156 and 157, side switch wiper 130,

ringer relay springs 197 and 196, condenser 148 to the calling subscribers vertical line conductor 38, over circuits that have been described, through the receiver 2 back to the vertical line conductor 38, thence to the rotary trunk conductor 90 to the rotary line relay 125 of the connector, to the battery lead 17-1 and back to the busy signal coil 155. The calling subscriber upon hearing the busy signal releases his switching apparatus at the central olfice.

It will be noticed that during the establishment of the connection between the substation A and the connector F the line relays 40 and 41 of the first-selector B, and the line relays 117 and 118 of/the second-selecfor G, are retained across the line. It follows, therefore, that even after the selector D establishes connection with the repeater C the line relays 10 and 41 become energized, respectively, when the line conductors 38 and 39 are grounded. The energization of said relays is of no consequence, however, after the side switch passes to third position. The same is true of the second-selector G after the side switch passes to third position. It will be shown, however, that the said selectors B and G are dependent for their release upon the operation of their line relays when the line conductors 38 and 39 are grounded simultaneously. The release occurs when the calling subscriber restores his receiver 2 and presses the release springs 31, 32 and 33 into contact, thus simultaneously grounding the vertical and rotary line conductors 38 and 39 for a moment. Grounding the vertical and rotary line conductors 38 and 39 simultaneously energizes the vertical and rotary line relays 79 and 80 of the repeater C at the same time, whereby the springs 83 and 81 and 87 and 88 are pressed into contact at the same time. Also, as a result, the line relays 40 and 41 of the selector B energize over known circuits at the same time. The line relays 40 and 41 of the first-selector B being energized at the same time, the springs 162 and 167 are carried into engagement with the ground spring 163. The engagement of the springs 167 and 163 energizes the private magnet 49, which latter then presses the springs 164 and 164 into contact, thereby placing the release magnet 68 in connection with the spring 162. Therefore, since the spring 162, as has been stated, is in contact with the ground spring 163 a circuit is completed through the said release magnet 68 in which the current flows from ground G through the springs 163 and 162 and through the private springs 164 and 164; to the release magnet 68, thence to the battery lead 161 and through battery B to ground G The release magnet 68 being thus energized remains in readiness to restore the selector switch B when the subscriber at the substation A permits the release springs 31, 32 and 33 to separate. Of course the energization of the vertical and rotary line relays 79 and 80 of the repeater C grounds the vertical and rotary trunk conductors 89 and 90 that connect the repeater C with the exchange #2. The vertical and rotary trunk conductors 89 and 90 being grounded at the same time cause, as previously exnlained, the vertical and rotary line relays 121 and 125 of the. connector F Fig. 2) to be energized at the same time. Therefore, the line relay springs 188 and 189 and 215 and 216, and the private springs 190 and 176 are closed at the same time, so that an energizing circuit is established through the release magnet 129 of the connector F.

maaeoe G through the springs 189 and 188, private springs 190 and 176, and through the line relay springs 216 and 215, through the release magnet 129 to the battery lead 174, thence. through battery B to ground G". The connector release magnet thus energizes, releasing the connector-shaft and side switch at once. As soon as the subscribers release springs 31, 32 and disengage, the line relays -'10 and 41 of the selector B deenergize, releasing the selector B; also, the line relays 7 9 and 80 of the repeater C deenergize, leaving the repeater C fully restored and removing the ground connection from the trunk conductors 89 and 90. The removal of the ground connection from the trunk conductors 89 and 90 causes the deenergization of the rotary and vertical relays 117 and 118 of the selector G, and of the line relays 124 and 125 of the connector 1*. As soon as the line relays 117 and 118 of the selector G de'energize, the said switch G becomes restored; also, the deenergization of the line relays 124 and 125 of the connector F leaves the said switch fully restored. The restoration of the switch G is brought about in a manner similar to the restoration of the switches B and Fthat is, when the line relays 117 and 118 are energized simultaneously, an energizing circuit is established through the release magnet 99. This circuit extends from ground through the springs 121 and 119, private magnet springs 107 and 106 (bearing in mind that the private magnet is energized at this time), and through the release magnet 99 to the battery lead 174.

Returning now to the point Where the called subscribers bell is rung, it will be assumed that the called subscriber answers by removing his receiver 225, thus bridging his secondary circuit, including said receiver and the secondary winding 226 in series, across the called subscribers line. The subscribers thus become connected over the heavily marked conductors shown in Figs. 1 and 2, which conductors have been pointed out. After they are through communieating the calling subscriber may destroy the connection by hanging up his receiver 2, thus grounding the vertical and rotary line conductors 38 and 39 simultaneously as before. As a result the line relays of the first-selector B and the line relays 79 and 30 of the repeater C become energized simultaneously, as previously described when the calling subscriber released after receiving the busy signal. The line relays 7 9 and 80 of the repeater (J in turn ground the trunk conductors 89 and 90 simultaneously, thus in turn causing the energization of the line relays of the secondselector G and the connector F, as before. The connector-switch is, of course, thus released, as previously described, with the exception that in this case, since the switchshaft is rotated, the shaft first rotates to normal vertical position and then falls to its normal place. As soon as the shaft of the connector l is released from engagement with the trunk line leading to the called selector l) the private wiper 124 breaks connection with the private normal conductor 195, and as a result restoring the bridge-cut-ofi' relay 209 of the first-selector E, whereby the line relays 207 and 208 returnto their normal condition under the control of the substation D. As soon as the release springs 31, 32 and 33 separate, the ground connection to the conductors 38 and 39 is removed and as a result the first-Se lector B is restored and the repeater C is restored, which latter then removes the ground from the trunk conductors 89 and 90 and permitting as a result the selector G- and crnnector F to regain their full normal condition. If the called subscriber should desire to use his selector E before the calling subscriber A restores the switches he must first ground his line conductors 200 and 198 simultaneously by pressing the release springs 227, 228 and 229 together after the ground springs 230 and 231 have come into contact. As a result an energizing circuit is established through the back-bridge relays 1.46 and 147 of the connector F from ground G through the springs 230 and 231 to the ground release spring 229, thence to the vertical line conductor 198 by one path through the ringer relay springs 197 and 196, through the vertical back-bridge relay 146 to the battery lead 174, thence through battery B to ground G Over another branch thecurrent passes from ground release spring to the rotary line conductor 200, thence through the ringer relay springs 201 and 202 and through the rotary back-bridge relay 147 to the battery lead 174, and from battery 13 to ground G The said relays 146 and 147 upon energizing simultaneously force the springs 232 and 233 together and thus establish a circuit from ground G through the said springs 232 and 233 and through the release magnet 129 to the battery lead 174, and thence through battery B to ground G The connector F is released, the wipers 122, 123 and 124 disconnected from the first-selector E, and, therefore, the energizing circuit for the bridgecut-oif relay 209 destroyed, leaving the firstselector E and connector F fully restored. Having been restored the selector E may then he used by the subscriber at substation D. The calling subscriber may then, by grounding his line conductors 38 and 39, upon hanging up his receiver, restore the remaining switches B, C and G in a manner that is already known. The repeater C is adapted to be inserted in any part of the circuit either between the substation and the selector B, or between the second-selector G and connector F, or in any other position where the repetition of impulses is desirable, as in the case described. The resistance of the coils 79 and 80 may be of any suitable character, but good results are obtained when they are wound to five hundred ohms each. It will be evident that each time that the subscriber sends impulses over his line. conductors 38 and 39, after connection has been made with the repeater C, the condensers 91 and 92 will send kicks over the trunk line conductors 89 and 90 (if the connection is not interru ted) that might afi ect the relays of the switch at the other end of the line in such a way as to require a more particular or delicate adjustment of said relays. It is to reduce such a possibility as much as possible that the connection between the trunk line conductors 89 and 90 and the condensers 91 and 92 is made through the line relay springs 82 and 83 in one case, and 86 and 87 in the other case. Therefore, each time that the relays 79 and 80 are energized the connection is broken between the condensers and their allctted trunk lines.

By providing the repeater relays 79 and 80 with contacts controlling the line circuit of the trunks leading to the second-selector, less delicate or particular adjustment is necessary for the relay springs of the second-selector and connector, as well as for the impulse-transmitting mechanism of the calling subscriber, in order to reduce the liability of any uncertainty of action resulting from the kicks or static discharges from the condensers 91 and 92. In other words,

it is possible, of course, to so adjust the line relay springs, as well as the impulse-transmitting devices of the subscribers stations, that the static discharges from the condensers will be prevented from causing any confusion or uncertainty of action on the part of the second-selector and connector. With the provision of my improved repeater relays, involving an opening at the trunk line circuit each time one of the relays lS energized, such adjustment can be effected with considerably less particularity or delicacy, and certainty of operation is insured with less labor and care in installing and maintaining the system.

The intermittent opening and closin of the line circuit. which is accomplishe .by the relays 79 and 80 which constitute an impulse-transmitting mechanism, may be used for various purposes. My invention broadly contemplates, therefore, the provision of an impulse-transmitting mechanism which intermittently opens and closes the line circuit-that is to say, the talking circuitin orderv to transmit the calling impulses.

What I claim as my invention is 1. In a telephone exchange system, a plurality of automatic switches, a circuit leading thereto, a pair of relays provided with means for grounding said circuit and thereby successively controllin said automatic switches, each relay provi ed with normally closed contacts controlling the continuity of said circuit.

2. In a telephone exchange system, a trunk line circuit, a pair of relays bridged across the said circuit, automatic switchmachines controlled by said relays, a su scribers calling device for controlling the energizing of said relays, and a central source 0 operating current, each relay provided with normally closed contacts controlling the continuity of said circuit.

3. In a telephone exchange system, a line circuit, automatic switch mechanism, a relay connected with said circuit and controlling said automatic switch mechanism. over a portion of the line circuit, a subscribers device for controlling the energizing of said relay, and a central source of operating current, said relay provided with normally closed contacts controlling the continuity of said line circuit.

. 4. In a telephone exchange system, a line circuit, automatic switch mechanism, a relay connected with said circuit and controlling said automatic switch mechanism, a subscribers device for controlling the energizing of said relay, a central source of operating current, said relay provided with normally closed contacts controlling the continuity of said line circuit, together with normally open contacts and a ground connection for grounding said circuit when the relay is energized.

5. In a telephone exchange system, a firstselector, a second-selector, a trunk line connecting the first-selector with the secondselector, a repeater provided with relays controlling the continui y of the trunk line connection between the two selectors, a calling subscribers telephone line connected with said first-selector, a calling device by which the subscriber controls the first-selector, by which the second-selector is controlled through the medium of the repeater relays, ,a source of operating current, said repeater relays provided with normally open contacts and a ground connection for grounding the trunk line when the relays are energized.

6. In a telephone exchange system, a trunk line circuit, a pair of relays bridged across the said circuit, automatic switching machines controlled by said relays a subscribers calling device for control ing the energizing of said relays, and a central source of operatin current, each relay provided with normal y closed contacts controllid ling the continuity of said circuit, said relays being permanently connected with one pole of said source of operating current, the other pole of said source being grounded.

7. In a telephone exchange system, a line circuit,'automatic switch mechanism, a relay connected with said circuit and controlling said automatic switch mechanism over a portion of the line circuit, a subscribers device for controlling the energizing of said relay, and a central source of operating current, said relay provided with normally closed contacts controlling the continuity of.

said line circuit, said relay being permanently connected with one pole of said source of operating current, the other pole of said source being grounded.

8. In a telephone exchange system, a line circuit, automatic switch mechanism, a relay connected with said circuit and controlling said automatic switch mechanism, a subscribers device for controlling theenergizing of said relay, a central source of operating current, said relay provided with normally closed contacts controlling the continuity of said line circuit, together with normally open contacts, and a ground connection for grounding said circuit when the relay is energized, said relay being permanently connected with one pole of said source of operating current, the other pole of said source being grounded.

9. In a telephone exchange system, a firstselector, a second-selector, a trunk line connecting the first-selector with the secondselector, a repeater provided with relays controlling the continuity of the trunk line connection between the two selectors, a calling subscribers telephone line connected with said first-selector, a calling device by which the subscriber controls the first-se lector, by which the second-selector is controlled through the medium of the repeater relays, a source of operating current, said repeater relays provided with normally open contacts, and a ground connection for grounding the trunk line when the relays are energized, said relays being permanently connected with one pole of said source of operating current, the other pole of said source being grounded.

10. In a telephone exchange system, the combination of a trunk line, a pair of line relays bridged across the said trunk line, a condenser in each side of said trunk line, normally closed contacts in each side of said trunk line. said condensers beinglocated between the said relay bridge and the said normally closed contacts, normally open contacts and a ground connection for grounding the trunk line outside of the break therein produced by the opening of said normally closed contacts, a battery having one pole grounded and the other pole normally connected with the windings of said relays, means for closing circuit through said relays to energize the same, another battery having one pole grounded, an automatic switching machine proyided with relays normally connected with the other pole of said last mentioned battery, said last mentioned relays normally bridged across the said trunk line, said contacts all controlled by said first mentioned relays.

11. In a telephone exchange system, the combination of a trunk line, a relay connected therewith, a condenser in the trunk line, normally closed contacts in said trunk line, the said condenser being located between the relay and the said contacts, normally open contacts, and a ground connection for grounding the trunk line outside of the break therein produced by the opening of said normally closed contacts, a battery, and circuit connections for energizing said relay, all said contacts being controlled by said relay, whereby said trunk line is opened and then immediately grounded by the energizing of said relay.

12. In a telephone exchange system, the combination of a trunk line circuit, a plurality of automatic switching machines, a pair of relays bridged across said circuit, means by which a calling subscriber employs said relays for successively controlling said automatic switching machines, and a condenser in each side of said circuit, each relay provided with normally closed contacts controlling the continuity of said circuit, said condensers located between the relays and the said automatic switching machines, and said contacts located between said condensers and said automatic switching machines, said circuit opened when either relay is energized.

13. In a telephone exchange system, the combination of an automatic switching machine, a trunk line leading to said switching machine, a relay connected with the other end of the trunk line, a condenser associated with said relay and located in the trunk line circuit, and means for disconnecting the condenser from the switching machine when the relay is energized, together with means by which the relay grounds the trunk line after disconnecting the condenser.

14. In a telephone exchange system, the

- combination of a line circuit, a line relay, :1

to energize said relay, an automatic switch under the control of said relay, and means for opening said circuit each time the relay is energized, adapted to automatically close the same each time the relay is deenergized, together with means for grounding the circuit each time the relay is energized.

16. In a telephone exchange system, the combination of one exchange, another exchange, subscribers telephone lines terminating at each exchange, a trunk line ex tending between the two exchanges, and a repeater in said trunk line, said repeater provided with a relay having means for opening the trunk line each time it is energ 17. In a telephone exchange system, the combination of one exchange, another exchange, subscribers telephone lines terminating at each exchange, a trunk line ex tending between the two exchanges, and a repeater in said trunk line, said repeater having a pair of relays bridged across the trunk line, and provided with means for opending the same when either relay is enerize g 18. In a telephone exchange system, the combination of one exchange, another exchange, subscribers telephone lines terminating at each exchange, a trunk line extending between the two exchan es, and a repeater in said trunk line, sai repeater provided with a relay having means for opening the trunk line each time it is energized, together with means for grounding the I trunk line when the relay is energized.

19. In a telephone exchange system, the combination of one exchange, another exchange, subscribers telephone lines terminating at each exchange, a trunk line extending between the two exchanges, and a repeater in said trunk line, said repeater having a pair of relays bridged across the trunk line, and provided with means for opening the same when either relay is energized, together with means for groundin the trunk line when the relays are energize 20. In a telephone exchange system, the combination of one exchange, another exchange, subscribers telephone lines termi- 'nating at each exchange, a trunk line extending between the two exchanges, a repeater in said trunk line, said repeater provided with a relay having means for 0 ening the trunk line each time it is energized, and a condenser for each side of the trunk line, located between the said relay and the break produced in the trunk line by the energizing of said relay.

21. In a telephone exchange system, the combination of one exchange, another exchange, subscribers telephone lines terminating at each exchange, a trunk line ex tendin between the two exchanges, a repeater in said trunk line, said repeater hav- 1,12s,soe

ing a pair of relays bridged across the trunk line, and provided with means for opening the same when either relay is energized, and a condenser for each side of the trunk line, located between the said relays and the break produced in the trunk line by the energizing of said relays.

22. In a telephone exchange system, the combination of one exchange, another exchange, subscribers telephone lines terminating at each exchange, a trunk line extending between the two exchanges, a repeater in said trunk line, said repeater provided with a relay having means for opening the trunk line each time it is energized, together with means for grounding the trunk line when the relay is energized, and

a condenser for each side of the trunk line, located between the said relay and the break produced in the trunk line by the energizing of said relay.

23. In a telephone exchange system, the combination of one exchange, another exchange, subscribers telephone lines terminating at each exchange, a trunk line extending between the two exchanges, a repeater in said trunk line, said repeater having a pair of relays bridged across the trunk line, and provided with means for opening the same when either relay is energized, together with means for grounding the trunk line when the relays are energized, and a condenser for each side of the trunk line, located between the said relays and the break produced in the trunk line by the energizing of said relays.

24. In a telephone exchange system, the combination of one exchange, another exchange, a trunk line connecting the two exchanges, an automatic switching machine at one end of said trunk line, a pair of relays at the other end of said trunk line, means by which the energizing of said re lays directly severs the trunk line, and means by which a calling subscriber employs said relays for controlling said automatic switching machine.

25. In a telephone exchange system, the combination of a trunk line, an automatic switch at one end of said trunk line, a pair of relays at the other end of said trunk line, means by which the trunk line is directly severed by the ener izing of said relays, and means by whic a calling subscriber employs said relays for controlling said automatic switch.

26. In a telephone exchange system, a talking circuit, a repeater having means for opening and closin a normally closed switch point in sai talking circuit, and switching means controlled by said repeater over a portion of the talking circuit, substantially as set forth.

27. In a telephone exchange system, a plurality of automatic switches, means which the second-selector a source of operating current, said maaaoe therein having one motion to select groups and another motion to connect with a line in any selected group, a circuit leading thereto, a pair of relays provided with means for grounding said circuit and thereby successively controlling said automatic switches, each relay provided with normally closed contacts controlling the continuity of said circuit.

28. In a telephone exchange system, a trunk line circult, a pair of relays bridged across the said circuit, automatic switching machines, means therein having one motion to select groups and another motion to connect with a line in any selected group and controlled by said relays, a subscribers calling device for controlling the energizing of said relays, and a central source of operating current, each relay provided with normally closed contacts controlling the continuity of said circuit.

29. In a telephone exchange system, a line circuit, automatic switch mechanism, means therein having one motion to select groups and another motion to connect with a line in any selected group, a relay connected with said circuit and controlling said automatic switch mechanism, a subscribers device for controlling the energizing of said relay, and a central source of operating current, said relay provided with normally closed contacts controlling the continuity of said line circuit.

30. In a telephone exchange system, a

first-selector, means therein having one motion to select groups and another motion to connect with a line in any selected group, a second-selector, a trunk line connecting the first-selector with the second-selector, a repeater provided with relays directly controlling the continuity of the trunk line connection between the two selectors, a calling subscribers telephone line connected with said first-selector, a calling device by which the subscriber controls the first-selector, by is controlled through the medium of the repeater relays,

repeater relays provided with normally open contacts and a ground connection for grounding the trunk line when the relays are energized.

31. In a telephone exchange system, the combination of a trunk line. a pair of line relays bridged across the said trunk line, a condenser in each side of said trunk line, normally closed contacts in each side of said trunk line, said condensers being located between the said relay bridge and the said normally closed contacts, normally open contacts and a ground connection for grounding the trunk line outside of the break therein produced by the opening of said normally closed contacts, a battery having one pole grounded. and. the other pole normally connected with the windings of said relays, means for closing circuit through said relays to energize the same, another battery having one pole grounded, an automatic switching machine, means therein having one motion to select groups and another motion to connect with a line in any selected group and provided with relays normally connected with the other pole of said last-mentioned battery, said last-mentioned relays normally bridged across the said trunk line, said contacts all controlled by said first-mentioned relays.

32. In a telephone exchange system, the combination of a trunk line circuit, a plurality of automatic switching machines, means therein having one motion to select groups and another motion to connect with a. line in any selected group, a pair of relays bridged across said circuit, means by which a calling subscriber employs said relays for successively controlling said automatic. switching machines, and a condenser in each side of said circuit, each relay pro vided with normally closed contacts controlling the continuity of said circuit, said condensers located between the relays and the said automatic switching machines, and said contacts located between said 0011- densers and said automatic switching maa5 chines, said circuit opened when either relay is energized.

33. In a telephone exchange system, the

combination of an automatic switching machine, means therein having one motion to mat select groups and another motion to connect witha line in any selected group, a trunk line leading to said switching machine, a relay connected with the other end of the trunk line, a condenser associated with said relay and located in the trunk line circuit, and means for disconnecting the condenser from the switching machine when the relay is energized, together with means by which the relay grounds the trunk line after dis- 11o connecting the condenser. I

34. In a telephone exchange system. the combination of a line circuit, a line relay, a subscribers calling device for transmitting electrical impulses over the line circuit to lit energize said relay, an automatic switch. means therein having one motion to select groups and another motion to connect with a line in any selected group and under the control of said relay, and means for open- 12:) ing said circuit each time the relay is energized, adapted to automatically close the same each time the relay is deenergized.

35. In a telephone exchange system, the combination of one exchange, another exchange, means therein having one motion to select groups and another motion to connect with a line in any selected group, subscribers telephone lines terminating at each exhanae a trurk ne. Wen ie-a. b e n he two exchanges, and a repeater in said trunk line, said repeater provided with a relay having means for opening the trunk line each time it is energized.

.36. In a telephone exchange system, the combination of one exchange, another exchange, means therein having one motion to 'select groups and another motion to connect with a line in any selected group, subscribers telephone lines terminating at one exchange, a trunk line extending between the two exchanges, and a repeater in said trunk line, said repeater having a pair of relays bridged across the trunk line, and provided with means for opening the same when either relay is energized.

37. In a telephone exchange system, the combination of one exchange, another exchange, a trunk line connecting the two exchanges, an automatic switching machine at one end of said trunk line, means therein having one motion to select groups and another motion to connect with a line in any selected group, a pair of relays at the other end of said trunk line, means by which the energizing of said relays'directly severs the trunk line, and means by which a calling subscriber employs said relays for controlling said automatic switching machine.

38. In a telephone exchange system, the combination of a trunk line, an automatic switch atone end of said trunk line, means therein having one motion to select groups and another motion to connect with a line in any selected group, a pair of relays at the other end of said trunk line, means by which the trunk line is directly severed by the energizing of said relays, and means by which a calling subscriber employs said relays for controlling said automatic switch.

39., In a telephone exchange system, means therein having one motion to select groups and another motion to connect with a line in any selected group, and a repeater having means for opening and closing anormally closed switch point in the talking circuit'established by -the said two motions, substantially as set forth.

40. In a telephone system, a trunk line,

a repeater including a relay having normally closed contacts in the pathof the voice-currents. and automatic selecting means controlled by said relay,

41. In "a telephonesystem provided with calling mechanisms at subscribers stations and automatic switches atthe central oflice for connecting subscriberslines for conversation. the combination of a telephone line connecting a substation with the central oflice, calling mechanism for said line at the substation, a central source of current for operating purposes. an automatic switch indi- .vidual to said line at the central oflice, a

trunk circuit at the central ofiice, electromagnetic means for operating said switch responsive to said calllng mechanism adapted to place said line in electrical connection with said circuit, electromagnetic switching devices associated with said circuit responsive to said calling mechanism when said circuit is connected with said line, a selector switch, a pair of conductors for said trunk circuit extending to said selector switch, a connector switch, electromagnets associated with said selector switch responsive to said switching devices for causing the operation of said selector switch to place said selector switch in electrical connection with said connector switch, electromagnets associated with said connector switch responsive to said switching devices when said switch is connected with said selector switch for causing the operation of said connector switch to place it in electrical connection with the line of a called subscriber, and means for opening the talking circuit each time a calling impulse is transmitted and repeated over the said circuit.

42. In a telephone system provided with calling mechanisms at subscribers stations and automatic switches at the central office for connecting subscribers lines for conversation, the combination of a telephone line connecting a substation with the central oflice, calling mechanism for said line at the substation, a central source of current for-operating purposes, an automatic switch individual to said line at the central otlice, a trunk circuit at the central ofiice. electromagnetic means for operating said switch responsive to said calling mechanism adapted to place said line in electrical connection with said circuit. electromagnetic switching devices associated with said circuit responsive to said calling mechanism when said circuit is connected with said line, a selector switch, a pair of conductors for said trunk circuit extending to said selector switch, a connector switch, electromagnets associated with said'selector switch responsive to said switching devices for causing the operation of said selector switch to place said selector switch in electrical connection with said connector switch, electromagnets associated with said connector switch responsive to said switching devices when said switch is connected with said selector switch for causing the operation of said connector switch to place it in electrical connection with the line of a called subscriber, release mecha-, nism for disconnecting said automatic switch. said selector switch and said connector switch, responsive to said switching de-' vices when the telephone line is switched for conversation, and means for opening the talking circuit each time a calling impulse is'transmitted and repeated over the said circuit.

43. In a telephone exchange system 'pro- -vided with calling mechanisms at subscribers stations and automatic switches at the central office for connecting subscribers lines for conversation, the combination with a telephone line connecting a substation with the exchange, of calling mechanism for said line at the substation, a pair of relays at the exchange adapted to be controlled by means of said mechanism, a selector switch -with the exchange, of calling mechanism for said line at the substation, a pair of relays at the exchange adapted to be controlled by means of said mechanism, a selector switch and a connector switch adapted to be successively operated, responsive to said relays, in establishing desired connections and mechanism adapted to be operated responsive to said relays when disconnection is desired for releasing said switches, and means for opening the talking circuit each time a calling impulse is transmitted and repeated over the said circuit.

45. In a telephone exchange system provided with calling mechanisms at subscribers stations and automatic switches at the central oflice for connecting subscribers lines for conversation, the combination with a telephone line connecting a substation with the exchange, of calling mechanism at the substation, a pair of relays at the exchange adapted to be controlled by means of said mechanism, a selector switch and a connector switch adapted to perform successive switching operations in connecting said line with a desired line, electromagnets for operating said selector switch adapted to be controlled by said relays and electromagnets for operating said connect r switch adapted to be controlled by said rela s, and means for opening the talking circuit each time a calling impulse is transmitted and repeated over the said circuit.

46. In a telephone exchange system provided with calling mechanisms at subscribers stations and automatic switches at the central oflice for connecting subscribers lines for conversation, the combination with a telephone line extending from a substation to the exchange, of calling mechanism at the substation adapted, under control of the subscriber. to effect the transmission of currents over the line, electromagnets at the exchange adapted to be controlled by means of said calling mechanism, conductors associated therewith and switching apparatus controlled by said electromagnets adapted to transmit currents over said conductors, a selector switch, contacts included in the mechanism thereof forcontinuing the circuit of said line to a desired line, electromagnets for operating said switch adapted to be controlled by currents transmitted over said conductors by said apparatus after said selector switch is operated, and means for opening the talking circuit each time a calling impulse is transmitted and repeated over the said circuit.

47. In a telephone exchange system provided with calling mechanisms at subscribers stations and automatic switches at the central ofiice for connecting subscribers lines for conversation, the combination with a calling subscribers line connecting the substation with the exchange, of calling mechanism for the line at the substation. repeating relays at the exchange adapted to be c ntrolled b means of said mechanism, a called subscribers line and a selector switch and a connector switch at the exchange adapted to successi ely c operate with said relays in connecting said lines,

and means for opening the talking ci cuit each time a calling impulse is transmitted and repeated over the said circuit.

48. In a telephone system, a talking circuit, means for transmitting calling impulses over conductors of said talking circuit. in accordance with the digits of the called number. and a repeater including relays at a central station for opening said circuit each time an impulse is transmitted.

49. In a telephone system. a tal ing circuit, means for transmitting calling impulses over c nductors of said circuit. in accordance with the digits of the called number, and a repeater provided with means responsive to said impulses to open the circuit each time an impulse is transmitted.

50. In a telephone system. a line circuit, means for transmitting calling im ulses over said circuit. in accordance with the digits of the called number, means for repeating said impulses from one portion of one side of said circuit to another p rtion thereof, and means responsi e to said impulses to open the said circuit each time an impulse is transmitted.

51. In a telephone system. a talking circuit, and means for transmitting electrical impulses over conductors of said circuit. in accordance with the digits of the called number, comprising relays at a central station for intermittently opening the said circuit.

52. In a telephone system, a talking cirthe central oflice which, in the transmission of said impulses, must intermittently open Signed by me at Chicago, Cook county, and close a conductor of said talking cir- Illinois, this 27th day of Jul 1906. cult, and automatic switching means respon- JOHN RICKSON. sive to said impulses, said automatic switch- Witnesses;

5 ing means having motion in two intersect- BERNARD D. WILLIs, ing planes. EDWARD D. FALEs. 

